The invention relates to a film which has a replication lacquer layer with a diffractive relief structure formed thereupon as well as a transparent colour lacquer layer, a security paper, a value document and a transfer film with such a film, as well as a production process for such a film.
It is known to equip value documents with security elements which, in the form of flexible film elements, display a diffractive, optically variable effect. This can be achieved by a surface relief structure which is stamped in a replication lacquer layer and the visibility of which is improved by provision of a reflective layer, in particular in the form of a reflective metal surface. Such security elements are quite generally classed with so-called OVDs (OVD=Optically Variable Device). Additional features of such security elements such as coloured areas are desirable for protection against forgery and for aesthetic reasons. For this, the replication lacquer layer can be dyed. However, this technology reaches its limits when multicolour diffractive elements or high flexibility in terms of colouring is desired.
U.S. Pat. No. 5,714,231 A (see also DE 4313521 A) relates to the provision of structures with an optical-diffraction effect only in a region-wise manner, corresponding structures are thus to be destroyed in order to prevent the diffractive effects in a region-wise manner. As a solution, it is proposed to completely emboss a decorative layer and then to apply a cover lacquer layer in areas where no optical-diffraction effect is to be provided. An observer forms the impression that the structure is present only in the desired region, in particular because depressions and raised portions are leveled off. Furthermore, a reflecting layer is also provided above the lacquer layer. The reflecting layer is also substantially flat in areas where the cover lacquer layer is present.